Process for the digestion of vegetable growths to produce cellulose



Patented June 18, 1935 PATENT oFricF.

rnocess Fort THE DIGESTION or VEGE- Y TABLE oaow'rns 'ro rnonoos CELLU- LOSE Herman" Kipper, Accord, Mass.

--No Drawing.lApplication April 13, 1933, I i SerlalNo. 665,957 r '9' Claims. (01192-9) In my copending application, 'Serial*#660,649,

of March 14, 1933,I describe processing for the digestion or decomposition of wood, for secural of cellulose fibre by means of'nitric acid thoroughly mixed with or disseminatedthroughout a-liquid as carbontetrachloride'. Sixty percent fuming nitric acid was employed most advantageously by me since its specific gravity and that of carbontetrachloride vary but little, so that comingling 10 of the two liquids was readily brought about. In

using nitric acid with benzol, the'requisite conditions were not as easilyestablished. Recently, however, I have brought about comingling or thorough mixing of the latter liquids by what,'I believe, has been termed a turbo mixer, that is apparatus in which rapidly traveling metal blades produce mixing of the liquids within a closed metal cylinder. The liquids thus thoroughly mixed were allowed to flow directly into the digester which had been previously filled with the wood chips. Very satisfactory digestion was then secured when using about twenty percent of nitric acid on weight of dry wood. The benzol used'was about three to'oneon theweight of dry wood. Digestion was carried out either coldor hot in a type of digester described in my Patent 1 #1320376 of August 25, 1931.

After digestion, the benzol was first drawn off by suction from the digester and then a hot dilute caustic soda'solution'was run into the digester.

The benzol contained in the digested organic material' was thereby volatilized and condensed by cooling coils situated externally'to the. digester. After treatment with the hot caustic solution, the latter was also drawnofi by suction from the digester and the cellulose fibre washed with water, either hot or cold, with possible finally slightly acidified water.

I have also brought about digestion in the type 40 or digestr above described when using carbontetrachloride and oxygen, without the use of nitric acid. The digestion is bettered by first admitting steam to the digester to the extent of twenty to forty percent on the weight of dry wood. or course other percentages of water may be em ployed. The digestion was carried out under about a hundred pounds pressure of oxygen under the conditions above noted and with hot carbontetrachloride, although even cold can be satis- Iactorily used. Subsequent drawing off and volatilization of the carbontetrachlorlde and final treatment with an aqueous hot caustic soda solution were carried out as usual. Only one set of traveling metal bars were: used in the digester were brought nearly to the bottom of the digester, or just ab'ovethe screen at the outlet of the digester'and' also situated close to its bottom,'these blades tend tolreepthe screen free of excess pulp or fibre, so ,that the liquids, .ascarbo-ntetrachlo- 5 ride, etc; are readily drawn ofi; through. such screen. In the latter arrangement, the shaft carrying the heater blades or bars were situated not centrally to the digestion cylinder, butbetween its centre and circumference.

Similar digestions were made with benzol and other coal tardistillates and with water and alcohols. The higher alcohols, as propyl, butyl and amyl, peculiarlyv become miscible with water from the resinextracted from the wood, so'that 15 such solution ofresin can be used directly in the pulp beater. 'In' carrying outthis work with the use of benzol, the wood was first steamed to about a twenty to forty percent content of water before digestion with the organic. liquid, al- 20 though in the ease of the loweralcohols, such as methyl and ethyl, the waterand alcohol may. be more readily simply first mixed together:- I also used ammonia when employing the alcoholsas a lurther'diges'tion aid, and likewise carried out 25 several digestions with bonzol and the alcohol aqueous mixture inan atmosphere of hydrogen 'at about one hundred pounds pressure.- Subcarried out at superatmospheric pressure, about 40 one hundred and twenty five pounds, whereas I use in the final digestion only a hot aqueous solution at atmospheric pressure.

Digestions of waste cotton seed hulls for se curing the fibre content were carried out very 45 similarly to those already described. A larger percentage or chemicals, however, were required for their digestion, for instance, about thirty percent of nitric acid. As noted in my copending application I have carried out digestion with 60 other vegetable growths than wood or cotton seed hulls and secured analogous results. My complete series of experiments, however, were conducted with wood, a fair percentage oi? same were likewise applied to cotton seed hulls ends few digestions made with other fibres. In view of similarity in all of these digestions or ex- 1 periments I feel that I have 2. Just basis for claiming the basic principles of digestion or of extraction to all vegetable growths.

My apparatus was built either of steel or of an iron-nickel-chromium alloy. Acid corrosion of the former appeared very slight but no doubt for continuous operation the alloy would be preferable.

My three steps of development or of invention cover, first a cheap method of digestion or of destruction of the resin content of wood or of other vegetable growths, with nitric acid, and recovery of the cellulose fibre, secondly a further reduced cost in resin destruction because otthe use of oxygen (air), or combinations of the two steps, and finally the disintegration or digestion of the wood with the recovery of the resinous material as well as the cellulose fibre.

I claim;

1. In a. process for the digestion of vegetable gro'wthsto secure cellulose fibre, the step of subjecting the said growths tothe action-f nitric acid mixed with organic liquids. i 2. In a process for. the digestion of vegetable growths to secure cellulose fibre the step of sub jectingthe said growths to the action of turning nitric acid mixed with organic liquids.

3. In a processifor the digestion of vegetable growths to secure cellulose fibre the step of subjecting the said growths to the'actio'n of nitri acid mixed with benzol.

4. In a process for thedigestion of vegetable growths to secure cellulose fibre the step of subjecting the said growths to the action of nitric acid and benzol and subsequently treating the residual material after drawing off of the benzol with a hot aqueous solution of sodium hydroxide.

5. In a process for the digestion of vegetable growths to secure cellulose fibre the step of sub- Jecting the said growths to the action of nitric acid. mixed with benzol and the step of disintegrating the said vegetable material mechanically by the.action of cylindrically rapidly moving metal pieces'simultaneously with the process of digestion, and, after withdrawal of the benzol, the step of subsequently treating the residual material from such digestion with a hot aqueous solution of sodium hydroxide and simultaneously subjecting the products of the digestion to the action of cylindricaliy rapid moving metal pieces.

6. In a process for the digestion of vegetable growths to secure cellulose fibre and for extraction of resinous matter, the step of subjecting the said growths to the action of organic liquids extraneous to the naturally occurring vegetable fibre constituents obtained by aqueous digestion and the step of disintegrating the said vegetable material mechanically by the action of cylindricaliy rapidly moving metal pieces simultaneously with the process of digestion or of extraction.

7 In a process for the digestion of vegetable growths to secure cellulose fibre and for the extraction oiresinous matter, the step of subjecting the said growths to the action of benzol and the step of disintegrating the said vegetable material mechanically by the action of cylindricaliy rapidly moving metal pieces simultaneously with the process or of'extraction.

8. In a process for the digestion of vegetable growths to secure cellulose fibre and for the extraction of resinous matter the step of subjecting the said growths to the action of water and benzol above its boiling point and at super-atmospheric pressure and the step of disintegrating the said vegetable material mechanically by the action of cylindricaliy rapidly moving metal pieces simultaneously withthe process of digestion or of extraction and, after withdrawal of the benzol, the step of subsequently treating the residual material from the said digestion or extraction with a hot aqueous solution of sodium hydroxide and simultaneously disintegrating such residual material mechanically by the action of cylindricaliy rapidly moving metal pieces and finally the suitable washing of the cellulose fibre thus produced.

9. In a process for the digestion of wood to secure cellulose fibre and for the extraction of resinous matter the step of subjecting the wood cut into chips to the action of water and of benzol above its boiling point andv at super-atmospheric pressure and the step of disintegrating the said pieces of wood mechanically by the action of cylindrically rapidly moving metal pieces simultaneously with the process of digestion or of ex traction and after withdrawal of the benzol the step of subsequently treating the residual material from the said digestion or extraction with a hot aqueous solution of sodium hydroxide and simultaneously disintegrating such residual material mechanically by the action of cylindrically rapidly moving metal pieces and finally suitably washing of the cellulose fibre thus produced.

- HERMAN B. KIPPER. 

